In recent years, the spread of resource exploration devices in the sea or marine earthquake sensor networks for early detection of earthquakes has progressed and there has been a high need for electric power supply means for these devices. It is desirable to use wireless electric power transmission technology as the electric power supply means for these devices because they are surrounded by seawater. This is because enabling wireless transmission of electric power obviates the need to expose a metal plug for electric power supply and the possibility of short-circuiting in seawater, which has a conductivity of about 4 siemens per meter (S/m).
In general, a coil obtained by winding a wire a plurality of times is used as means for wirelessly transmitting and receiving electric power. A magnetic flux interlinking the coil is generated by applying alternating current (AC) power to the coil of the power transmitting unit. Further, this magnetic flux generates an induced current in the coil of the power receiving unit by performing interlinking with the coil of the power receiving unit and the transmission of electric power is performed.
Incidentally, in wireless technology, for example, technology for performing communication between a terminal device main body and a detachable electronic device such as a memory card using a wireless millimeter wave signal is disclosed in Patent Document 1. In addition, technology for improving inductance values of a power transmitting unit and a power receiving unit and increasing a distance of electric power transmission using a magnetic member is disclosed in Patent Document 2. In addition, technology for improving mutual inductances of a power transmitting unit and a power receiving unit and increasing a distance of transmission by causing resonance (magnetic field resonance) at the same frequency using a coil having a high quality (Q) value is disclosed in Patent Document 3.